The invention is directed to methods of determining a reuse period for a chemical disinfectant composition and methods of reusing a high level disinfectant without retesting efficacy of the active ingredient.
Instruments that are used in diagnostic or therapeutic procedures, which encompass surgical, medical, dental, etc. procedures, require decontamination to remove microbial contamination. Depending upon the ultimate use of the instrument, different degrees of decontamination are required.
As used herein, decontamination is the removal of hazardous or unwanted materials such as bacteria, mold spores or other pathogenic life forms and the like, wherein high-level disinfection and sterilization represent different levels of decontamination. Sterilization is a level of decontamination representing the complete elimination or destruction of all forms of microbial life, including fungal and bacterial spores. High-level disinfection is a level of decontamination representing elimination of many or all pathogenic microorganisms, with the exception of bacterial spores, from inanimate objects.
Regulatory agencies and other groups have classified medical devices, processes, and cleaning and decontaminating products according to basic principles related to infection control. Medical devices are classified as critical, semicritical or noncritical. Critical devices, for example, scalpels, needles and other surgical instruments, enter sterile tissues or the vascular system. Such devices require sterilization with a process or with prolonged contact with a sporicidal chemical prior to reuse. A common way to sterilize critical devices is by exposure to heat. However, some instruments such as flexible lensed endoscopy instruments, inhalation therapy equipment, and other instruments and materials cannot withstand heat and must be treated with chemical solutions to achieve disinfection or sterilization. Such chemical solutions have included aldehydes, such as glutaraldehyde or o-phthaldehyde, or peracids.
Semicritical devices, for example, flexible endoscopes, bronchoscopes, laryngoscopes, endotracheal tubes and other similar instruments, are those that may contact any mucous membranes except dental mucous membranes. Such devices require high-level disinfection with a process or short contact with a sporicidal chemical prior to reuse. High-level disinfection can be expected to destroy all microorganisms with the exception of high numbers of bacterial spores. A Food and Drug Administration (FDA) regulatory requirement for high-level disinfectants is 100% kill of 100,000 to 1,000,000 (105-106) organisms of Mycobacterium tuberculosis (M. tuberculosis) in the presence of 2% horse serum in a quantitative tuberculocidal test. An additional FDA regulatory requirement for high-level disinfectants is that they must also achieve sterilization over a longer exposure time than the disinfection regimen time. Common high-level disinfectants include glutaraldehyde solutions between 2.4-3.4%w/v which also typically require activation with an alkaline buffer just prior to use, acidic hydrogen peroxide (H2O2) at 7.5%w/v (for example, Sporox(copyright), Reckitt and Colman, Inc.), and an acidic mixture of 1.0%w/v H2O2 and 0.08%w/v peracetic acid (PAA) (Peract(trademark) 20, Minntech Corp. or Cidex PA(copyright), Johnson and Johnson). The minimum effective PAA concentration for high-level disinfection at 25 minutes (min) and 20xc2x0 C. is 0.05%w/v (500 ppm) (Peract(trademark) 20). The minimum effective H2O2 concentration for high-level disinfection at 30 min and 20xc2x0 C. is 6.0%w/v (Sporox(copyright)).
High-level disinfecting solutions are typically designed for a reuse option, depending upon the type of device treated with the solution. The FDA currently approves the period during which a high level disinfectant may be reused. For example, the FDA has authorized a glutaraldehyde high-level disinfecting solution for endoscope reprocessing to be reused for as long as 28-30 days. The principle reason for reusing a solution is economic, as the practice itself provides the opportunity for adding to the risk of transmission of infection. The practice of reusing a high level disinfectant solution often results in a slow, continuous dilution of the solution over time, due to the inadvertent carry-over of rinse water into the disinfection solution. This rinse water may be present due to precleaning and rinsing prior to disinfection.
Medical devices such as thermometers and hydrotherapy tanks are also classified as semicritical, but they require intermediate-level rather than high-level disinfection prior to reuse. Intermediate-level disinfection inactivates M. tuberculosis, vegetative bacteria, most viruses and most fungi, but does not necessarily kill bacterial spores. A common intermediate-level disinfectant is Cavicide(copyright) (Metrex Research Corp.), which contains 0.28%w/v diisobutylphenoxyethoxyethyl dimethyl benzyl ammonium chloride, (a so-called super quat) and 17.2%w/v isopropyl alcohol.
Noncritical medical devices, for example, stethoscopes, tabletops, bedpans, etc., touch intact skin and require low-level disinfection prior to reuse. Low-level disinfection can kill most bacteria, some viruses, and some fungi, but it cannot be relied upon to kill resistant microorganisms such as tubercle bacilli or bacterial spores. Contact lenses are included in the class of devices which require low-level disinfection prior to reuse. Common low-level disinfectants for contact lens disinfection include acidic 3.0%w/v H2O2 and 1-10 ppm solutions of polymeric antimicrobial biguanides or quaternary ammonium compounds (e.g., 1 ppm polyhexamethylene biguanide in Complete(copyright) (Allergan Pharmaceuticals, Inc.) or 10 ppm Polyquad(trademark) polyquaternary ammonium compound in Optifree(copyright) (Alcon, Inc.).
Standards for sterilization and low, intermediate and high-level disinfection have been concurrently established. These standards are based upon the known or possible risk of contamination of a particular medical device by a particular microorganism, the pathogenic nature of the organism and other principles in infection control. They typically require demonstration of sterilization and/or disinfection efficacy against a particular panel of test organisms, which collectively represent the known or possible contamination and infection risks. The test panels and criteria are different for low, intermediate or high-level disinfection. It is also generally accepted that a high-level disinfectant will meet the disinfection efficacy standards of intermediate and low-level disinfection as well. It is universally accepted that low-level disinfection performance cannot predict intermediate or high-level disinfection performance. In fact, it is assumed prior to testing that a low-level disinfectant cannot achieve a higher level disinfection standard. Additionally, other factors such as device compatibility with the disinfection system must also be considered. The current medical device industry practices for semicritical medical devices (i.e., those that contact intact skin and all but dental mucous membranes) such as endoscopes involve separate short cleaning and disinfecting steps and times, and reusable solutions. Longer soak cleaning or disinfecting times and single-use solutions would for the most part be impractical and uneconomical in the current environment.
Currently, the only way to be assured that a high level chemical disinfectant is, in fact, achieving high level disinfection is by daily monitoring of the disinfectant solution. For example, the solution may be monitored by using a test strip that is impregnated with or otherwise contains chemicals reactive with one or more active components of the solution. Generally, a color reaction occurs in the presence of a threshold concentration of a chemical decontaminant, which indicates to the user that the chemical is at a concentration sufficient to achieve its stated level of decontamination. This concentration is frequently reported as the minimum effective concentration (MEC). The results are generally qualitatively indicated to the user as either xe2x80x9cpassxe2x80x9d or xe2x80x9cfailxe2x80x9d as the user interprets the color change on the strip.
The use of chemical test strips to monitor the effectiveness of a decontaminant composition has inherent problems. One problem is that it adds another step to the process, adding cost, time, and another variable in which errors may occur. It also may not provide an accurate assessment of the composition efficacy. For example, a chemical test strip is used to monitor effectiveness of an acidic hydrogen peroxide (H2O2) solution at a concentration of 6.0%w/v or greater (Sporox I(copyright) and Sporox II(copyright), Reckitt and Colman, Inc.). The reaction indicating effectiveness is based on the oxidation of iodide to iodine by the peroxide present in the composition. The strip contains iodide, horseradish peroxidase as the enzyme, and tetramethylbenzidine as the substrate. A blue color is produced on the strip in the presence of hydrogen peroxide at a concentration as low as 6.0%. However, the use of hydrogen peroxide alone at a concentration of up to 7.5% does not kill M. tuberculosis. Sporox I(copyright) and Sporox II(copyright) contain other excipients believed to be peracids, which are responsible for the tuberculocidal activity of the solutions. In fact, the manufacturer states that the test strip does not confirm disinfection or sterilization, and only indicates concentrations of hydrogen peroxide. The manufacturer also states that the test strip will give a xe2x80x9cpassxe2x80x9d result with any substance which will oxidize iodide to iodine and which is of sufficient strength. These substances include, among others, hypochlorite (bleach) and peracetic acid. Thus, this test strip is not specific for the active tuberculocidal component present in this disinfectant, nor does this test strip indicate the concentration of this component in the disinfectant.
In a disinfectant composition containing an acidic mixture of 1.0%w/v H2O2 and 0.08%w/v peracetic acid (PAA) (Peract198  20, Minntech Corp. or Cidex PA(copyright), Johnson and Johnson), a test strip is used to monitor the MEC. However, this test strip yields a positive result even in the absence of the peracetic acid component, and will indicate efficacy even if only the hydrogen peroxide component of the composition is present. Thus, even though the composition utilizes both hydrogen peroxide and peracetic acid to achieve effective decontamination, the user of the test strip will be erroneously assured that the composition is effective even if its peracetic acid component is below its effective concentration or is missing altogether. As an additional troublesome factor, it is the peracetic acid component that is the principle tuberculocidal entity in the composition.
The effectiveness of an o-phthaldehyde-containing composition (Cidex(copyright) OPA, Johnson and Johnson) is also monitored using a test strip. This test strip will yield a positive result in the presence of any aldehyde, and therefore is not specific for the active o-phthaldehyde component. The manufacturer specifically states that the test strips cannot be used to validate the sterilization or disinfection process. So as before, the user may be mistakenly assured of the efficacy of the composition when, in fact, the composition is below the MEC due to a missing, altered, or inactive component.
It would thus be desirable to provide a non-chemical method for determining the reuse period for a high level disinfectant solution. The method would eliminate the use of test strips to monitor efficacy of the solution, with their attendant problems of additional procedures, costs, and potential sources of error. The method would also eliminate the problems of inaccurate results from the chemical test strip reactions. This invention is directed to such a method.
The invention is directed to a method of determining a period during which a high level disinfectant composition for a medical device may be reused without retesting the composition to determine efficacy of the active ingredient, and methods of reusing the composition without retesting.
In one embodiment of the method, the period is determined directly using an algorithm where the established or determined time period for reuse with testing, and during which the active ingredient remains at least at a minimum effective concentration (MEC) for high level disinfection, is reduced by a factor to determine a reuse period without the need for testing by dividing the established or determined time period by the factor. The factor is in the range of about 1.1 to 10.0. A factor of 1.1 provides a time period during which the active ingredient is present at about a 10% excess of the MEC. A factor of 10.0 provides about a 90% excess of the MEC. In another embodiment the factor is in the range of 1.25 and 5.
In another embodiment of the method, the period is determined indirectly using an algorithm where the difference in concentration between that used successfully at 100% of the labeled concentration of active ingredient and the minimum effective concentration is reduced by dividing by a factor to determine a reuse period without the need for testing. The reuse period here equals the time required for the active ingredient in the solution to reach this new lowest concentration based upon the new smaller differences in concentration from the 100% labeled concentrations. The factor is in the range of 1.1 to 10.0.
The method may be used to disinfect the same device reused over the period, or different devices. The time may be established by a regulatory agency or may be established by testing.
The invention is also directed to a method of reusing a high level disinfectant, containing an active ingredient that is present in at least a minimum effective concentration, without retesting efficacy of the active ingredient. In the method, the time for reusing the disinfectant is limited to a time that is not more than about 90% of the time, or a concentration that achieves a time that is not more than about 90% of the time in which the active ingredient remains at least at the MEC.
The invention is also directed to a method to high-level disinfect a device with a reused high level disinfectant having at least one active ingredient over a time period without retesting to determine efficacy of the active ingredient over the time period. The maximum time period for reusing the disinfectant with testing is divided by a factor to determine the reduced time period for reusing the disinfectant without testing. In one embodiment, the factor is between 1.1 and 10.0. In another embodiment the factor is between 1.25 and 5.
Alternatively, the period is determined by dividing the difference in concentration between that used and the MEC by a number between 1.1 and 10.0 to determine the lowest concentration for reusing the disinfectant without testing, and then determining the time for the active ingredient in the composition to reach this concentration. The high level disinfectant is reused without retesting over this time period to achieve high level disinfection of the device. Many devices, for example, medical devices that have been reused on either the same or different patients may be disinfected over this time period.
The invention is also directed to a method of achieving high level disinfection of at least one medical instrument by reusing a high level disinfection composition containing an active ingredient in at least a minimal effective concentration without performing a test on the composition during the reuse period to determine efficacy of the active ingredient. A period of time during which the active ingredient remains above a MEC for high level disinfection is obtained, and that time is divided by a number between 1.1 and 10.0 to determine a reuse period for the composition.
Alternatively, the period is determined by dividing the difference in concentration between that used and the MEC by a number between 1.1 and 10.0 to determine the lowest concentration for reusing the disinfectant without testing, and then determining the time for the active ingredient in the composition to reach this concentration. The instrument is exposed to the composition without retesting for efficacy of the active ingredient during this reuse period at a time and temperature sufficient to achieve high level disinfection.
For any of these methods, the calculations may be performed manually, or a computer program may perform part or all of the algorithm for a particular device, protocol, organism, and/or composition.
The invention will be further appreciated in light of the following figures, detailed description, and examples.